Ceti Mensa (ctx frame - natural colors; credits: Lunexit)

This image shows a steep-sided depression in light-toned, layered rocks in the Valles Marineris Canyon System.
This formation, known as Ceti Mensa, is located in Western Candor Chasma in the Northern Valles.

The origin of Ceti Mensa and other Layered Deposits within the canyons is a source of much debate: proposed interpretations include lake deposits, deposits of volcanic ash, deposits of windblown sand and dust and glacial deposits. Recent spectral observations by the Mars Express and Mars Reconnaissance Orbiter Spacecraft have identified crystalline Iron Oxides and Hydrated Magnesium Sulfate minerals on Ceti Mensa.
These minerals are regarded as indicators of the presence of liquid water during their formation.

The Hydrated Sulfate mineral "Kieserite", in particular, most commonly forms on Earth by evaporation of brines.